General Anesthesia Practice Questions

Q: Which of the following medications should be dosed according to total body weight (TBW), instead of lean body mass in morbidly obese patients?

Succinylcholine. In morbidly obese patients, dosing medications is challenging due to changes in body composition (increased fat mass) and physiological shifts (increased blood volume and cardiac output). **Succinylcholine (Correct Answer):** Succinylcholine is the only neuromuscular blocker that must be dosed according to **Total Body Weight (TBW)**. In obesity, both the extracellular fluid volume and the activity of **pseudocholinesterase** (the enzyme that degrades succinylcholine) increase significantly. To ensure a rapid and effective neuromuscular blockade for intubation, the dose must be scaled to TBW (usually 1.0–1.5 mg/kg TBW). **Explanation of Incorrect Options:** * **Pancuronium & Vecuronium:** These are non-depolarizing neuromuscular blockers (NDMRs). Dosing them based on TBW in obese patients leads to excessive drug accumulation and prolonged paralysis because their clearance does not increase proportionally with weight. They should be dosed based on **Ideal Body Weight (IBW)** or **Lean Body Mass (LBM)**. * **Morphine PCA:** Opioids are highly lipophilic but can cause significant respiratory depression in obese patients (who often have underlying OSA). Dosing is generally based on **IBW/LBM** to avoid overdose and delayed recovery. **Clinical Pearls for NEET-PG:** * **TBW Dosing:** Succinylcholine, Dexmedetomidine, Neostigmine, and Maintenance dose of Propofol. * **IBW/LBM Dosing:** Non-depolarizing muscle relaxants (Vecuronium, Rocuronium), Induction dose of Propofol, Thiopentone, and Opioids (Fentanyl/Morphine). * **Key Rule:** For Succinylcholine, the increase in pseudocholinesterase activity is the primary reason for TBW-based dosing.

Q: Which of the following is NOT an aminosteroid non-depolarizing neuromuscular blocker?

Gantacurium. **Explanation:** Neuromuscular blocking agents (NMBAs) are broadly classified into two chemical classes: **Aminosteroids** and **Benzylisoquinolines**. **Why Gantacurium is the correct answer:** Gantacurium belongs to the **Benzylisoquinoline** class (specifically a chlorofumarate derivative). It is a newer, ultra-short-acting non-depolarizing agent designed to be degraded by non-enzymatic cysteine adduction and ester hydrolysis. Unlike aminosteroids, benzylisoquinolines are generally associated with histamine release but do not have the steroid nucleus. **Analysis of incorrect options:** * **Pancuronium:** A long-acting **aminosteroid**. It is known for its vagolytic effect, which can cause tachycardia. * **Pipecuronium:** A long-acting **aminosteroid** similar to pancuronium but without the significant cardiovascular side effects (vagolytic activity). * **Vecuronium:** An intermediate-acting **aminosteroid**. It is the mono-quaternary analog of pancuronium, lacks vagolytic effects, and is primarily excreted via bile. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Aminosteroids:** Remember the suffix **"-curonium"** (Pancuronium, Vecuronium, Rocuronium, Pipecuronium). * **Mnemonic for Benzylisoquinolines:** Remember the suffix **"-curium"** (Atracurium, Cisatracurium, Mivacurium, Gantacurium). * **Rocuronium** is the aminosteroid with the fastest onset, making it an alternative for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated. * **Sugammadex** is a specific reversal agent that works only for aminosteroids (Rocuronium > Vecuronium > Pancuronium) by encapsulation; it has no effect on Gantacurium or other benzylisoquinolines.

Q: Etomidate causes all of the following except:

Coronary insufficiency. **Explanation:** **Etomidate** is a carboxylated imidazole derivative used for the induction of general anesthesia. It is famously known for its **hemodynamic stability**, making it the induction agent of choice for patients with cardiovascular disease or shock. **Why Option A is the Correct Answer:** Etomidate **does not cause coronary insufficiency**. In fact, it maintains stable systemic blood pressure, heart rate, and myocardial oxygen delivery. It has minimal effect on sympathetic tone and does not cause histamine release, ensuring that coronary perfusion pressure is well-maintained. **Analysis of Incorrect Options:** * **B. Decreased steroidogenesis:** This is the most characteristic side effect of Etomidate. It causes dose-dependent inhibition of the enzyme **11-beta-hydroxylase**, which is essential for cortisol and aldosterone synthesis. This can lead to adrenocortical suppression even after a single dose. * **C. Decreased intracranial tension (ICT):** Etomidate is a potent cerebral vasoconstrictor. It reduces cerebral blood flow (CBF) and the cerebral metabolic rate of oxygen (CMRO2), which subsequently leads to a decrease in ICT. * **D. Nausea and vomiting:** Postoperative nausea and vomiting (PONV) is significantly more common with Etomidate compared to other induction agents like propofol. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For induction in patients with **valvular heart disease, coronary artery disease, or hypovolemia**. * **Myoclonus:** Etomidate frequently causes involuntary muscle movements (myoclonus) during induction, which can be attenuated by pre-medication with opioids or benzodiazepines. * **Solvent:** It is traditionally formulated in **propylene glycol**, which can cause pain on injection. * **Contraindication:** Relative contraindication in patients with **sepsis** due to its effect on the adrenal axis.

Q: Which of the following drugs produces a subjective feeling of well-being on emergence, thus conferring a potential for substance abuse?

Propofol. **Explanation:** The correct answer is **Propofol (Option B)**. Propofol is a short-acting intravenous anesthetic agent that acts primarily via the GABA-A receptor. It is unique among induction agents for producing a **subjective feeling of well-being, euphoria, and clear-headedness** during the emergence phase. This "pleasant" recovery is attributed to the release of dopamine in the nucleus accumbens (the brain's reward center). Consequently, Propofol has a documented potential for **substance abuse**, particularly among healthcare professionals with easy access to the drug. **Analysis of Incorrect Options:** * **A. Thiopentone:** A barbiturate that often causes a "hangover" effect or grogginess upon emergence. It does not typically produce euphoria. * **C. Etomidate:** Known for its cardiovascular stability, but it is associated with a high incidence of postoperative nausea and vomiting (PONV) and myoclonus, making the recovery period less pleasant. * **D. Ketamine:** Produces "dissociative anesthesia." While it can cause hallucinations, the emergence period is often characterized by **emergence delirium**, agitation, and vivid unpleasant dreams rather than a simple feeling of well-being. **High-Yield NEET-PG Pearls:** * **Propofol** is the drug of choice for Day Care (Ambulatory) Surgery due to its rapid metabolism and anti-emetic properties. * **Propofol Infusion Syndrome (PRIS):** A rare but fatal complication characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure (seen with high doses/long duration). * **Pain on injection** is a common side effect of Propofol (minimized by using larger veins or pre-treatment with Lidocaine). * **Egg/Soy Allergy:** Use caution, as Propofol is formulated in a lipid emulsion containing soybean oil and egg lecithin.

Q: What percentage of Halothane is metabolized?

25%. **Explanation:** The metabolism of volatile anesthetic agents occurs primarily in the liver via the **Cytochrome P450 (CYP2E1)** enzyme system. Among the potent inhalational agents, **Halothane** undergoes the most extensive hepatic metabolism. **1. Why 25% is Correct:** Approximately **20% to 25%** of Halothane is metabolized in the liver. This high rate of metabolism is clinically significant because it leads to the production of reactive intermediates (like trifluoroacetylated proteins). These metabolites can trigger an immune-mediated response, leading to **Halothane Hepatitis**, a rare but severe form of liver injury. **2. Analysis of Incorrect Options:** * **A (50%):** No commonly used volatile anesthetic reaches this level of metabolism. * **B (5%):** This is the approximate metabolism rate for **Sevoflurane** (2%–5%). * **C (2.50%):** This does not correspond to a specific major agent; however, **Enflurane** is metabolized at a rate of about 2%. * **D (25%):** This is the established high-yield value for Halothane. **3. High-Yield NEET-PG Clinical Pearls:** * **Metabolism Ranking (Highest to Lowest):** Halothane (25%) > Sevoflurane (2-5%) > Enflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Halothane Hepatitis:** More common in adults, females, and obese patients upon repeat exposure. * **Metabolite:** The oxidative metabolism of Halothane produces **trifluoroacetic acid**. * **Rule of Thumb:** Desflurane is the least metabolized (most stable), while Halothane is the most metabolized (least stable).

Question 1

Which of the following statements is true regarding Total Intravenous Anesthesia (TIVA) compared to inhalational anesthesia?

Accepted Answer

Reduces cerebral metabolism and cerebral blood flow.

Answer

Provides smooth induction with a high incidence of postoperative nausea and vomiting.

Answer

Propofol inhibits pulmonary vasoconstriction due to hypoxia and is associated with increased pulmonary toxicity, malignant hyperthermia, and enhanced N2O effects.

Answer

Associated with higher chances of nephrotoxicity.

Question 2

Which of the following medications should be dosed according to total body weight (TBW), instead of lean body mass in morbidly obese patients?

Accepted Answer

Succinylcholine

Answer

Pancuronium

Answer

Vecuronium

Answer

Morphine PCA

Question 3

A 32-year-old female presents with pain in the right lower iliac fossa and positive rebound tenderness. She underwent appendectomy under general anesthesia. Postoperative laboratory findings showed increased levels of transaminases with the absence of increased bilirubin. Which of the following anesthetic agents is most likely responsible for the elevation of the enzymes?

Accepted Answer

Halothane

Answer

Nitrous oxide

Answer

Methoxyflurane

Answer

Enflurane

Question 4

Which of the following statements regarding pancuronium is INCORRECT?

Accepted Answer

It is a vagal stimulant.

Answer

It is an aminosteroid skeletal muscle relaxant.

Answer

Cardiovascular side effects are common.

Answer

It is the second-longest acting neuromuscular blocker after doxacurium.

Question 5

Which of the following statements about sevoflurane is true?

Accepted Answer

It is nephrotoxic at high doses.

Answer

It has the maximum risk of causing convulsions.

Answer

It is cardiostable.

Answer

It can cause fulminant hepatitis.

Question 6

Which of the following is NOT an aminosteroid non-depolarizing neuromuscular blocker?

Accepted Answer

Gantacurium

Answer

Pancuronium

Answer

Pipecuronium

Answer

Vacuronium

Question 7

Etomidate causes all of the following except:

Accepted Answer

Coronary insufficiency

Answer

Decreased steroidogenesis

Answer

Decreased intracranial tension

Answer

Nausea and vomiting

Question 8

Which of the following drugs produces a subjective feeling of well-being on emergence, thus conferring a potential for substance abuse?

Accepted Answer

Propofol

Answer

Thiopentone

Answer

Etomidate

Answer

Ketamine

Question 9

What percentage of Halothane is metabolized?

Accepted Answer

25%

Answer

50%

Answer

5%

Answer

2.50%

Question 10

Depth of anesthesia by inhalation anesthetics depends upon which of the following factors?

Accepted Answer

All of the above

Answer

Respiratory minute volume

Answer

Solubility of the anesthetic agent in blood

Answer

Blood concentration of the anesthetic agent

General Anesthesia — MCQs

General Anesthesia — MCQs

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